Signaling system



c. s. R oADs SIGNALING SYSTEM Jan. 9, 1945. 2,367,054

Filed March. 24, 1944 IN VEN TOR c7. Sly/wads A TTORNE Y Patented Jan. 9, 1945 SIGNALING s-izs'rEM-v Kineri This invention rel-tee he signaling Systems and I more particularly-to signaling systems adapted to be used in conjunction with certain types of transmissionlines. Incertain types of transmission lines, for example linesused tointerconnect certain types of v offices in telephone systemathesupervisory signals ateach end of thezlinemay be controlled by current obtainedfrom 'a .gffounded commdn battery' supply.-. =Wi-thsuch asource' of supply a aircuit interconnecting two offices would bei supplied ,withvsupervisor'y sign-aling:current by aag -reunded battery connected at one office: to one side ofthe circuit, andground connected toxthe' ptherside thereof at; said" ofii'cej With such a'- type -9f groundedcommon batteryeircuit it-wou1d be very difiieu lt to make use of either of the conductors of the circuit in'dividual ly to provide an additional signaling circuit between the interconnected offices; as such use might involve grounding the chm ductor utilizedior such purpose-and this would interfere with the normai useof the circuit'for supervisory signaling; i-The primary object of the arrangements of the inventien is-t-provide an arrangement whereby one as the conductors of a circuit supplied with grounded" commcn' battery for supervisory signaling may beutilized in'divid nally te- :provideLan additional signaling circuit i without: any; interferencewiththe normal use of the; original circuit 'for. supervisory signaling;

the arrangementsrof-the invention, this isaccom plished by bridging aeliigh'"; resistance across the circuit at'ione endthereo'f and connecting its midpoint to the grid of a-three-element vacuum tube. Thetfiia'm'ent:of-such a tube would beg rbund'ed. Under such conditions the grounded common bat-- tery at the other end :of the circuit will apply 'a negative biasing voltage :to; the grid or the tube sufficient t block-it. Mea'n's would be provided atthe batter? end oft/the circuit to disconnect the grounded battery rromth eireuit an new; in its placeal-ndn-grounded batt lik (image. This would-cause no intei freficein th use-er the circuit for normal signalin'gipur pbsee but it w ould remove-the negative biasing voltagefiom the grid of' the tubeand' tliuSj cause it to operatel- Tl-ie plate circuit ofthe tube ceuldcentrol a d ed signal; Withs'ucn aniarran'gement'an addi enai signaling pathmay. pr vmeuhver' a; ef witheutcausing interference with the" normai use (if the c'ir'c'u Qther' objects and. reatureser the" inter-men W11 appear more fully mm the den-anew de's'cr i ptibrihereinatter L l s w I l I hate anuersm t uni: would include 'slipervis" eit the c Ts. ii hahus, Albany if from the following description together with the aecompanying drawing in the Figures 1 and- 2 of which the invention is illustrated; Fig; 1 is a'cifcuit diagram embodying a preferred; form-10f the invention. Fig.- 2 is a circuitdiagramillustrating certainprinciples'rof operation ofthe invention.

Similar i eferenceilcharacters have been used to denotellike parts" both figures f the invention. A In -Fig; 1 the arrangements of the invention are shnwn as applied to a; line L interconnecting tw'o telephone offices Aand B which lirie utilizes a cdzhmomgrounded battery 5' air supervisory sienailing purposes; O'fii'ce B might be a community ci-e11 office aha other; an central omce and the h e': name be termed eioop' am truhh; Such a sierra hg'a parating in theronewmg manner; Noreire-h-ih would he completed undd ee trai orhce battery 0mm hmty dial ofiie Iower wihdihe or i el ay 6& cdl'idubtor- Of line L, Y resista cewind e @and mwr'es tench windm a 'fpb 2 repay 4' at the c'entraloffic; tip condh th -of lirie L,j .'1.p15er winding of marginal relay at erdehdeabatte" 5 connected to the rin s de or the; and ground is eqhhehted to the tip see" of the linen. Due to the inclusion in the 'eireuit the high 'reslstanee w aihg of polar and cause it to,operate. The operation of relay Biwiliclose circuit gland; operate supervisory signal: apparatus atoflice B, Subsequent to the operation of th-is supervisory signal the subscriber answers and. circuit W will be closed at, oflice5B. This will cause the eperation' ofrelay 1 .whiohwill connect battery 5 to ,thetipside of the line'and ground;8Ktojthe-ring sideof the line and;thus reverse the direction of eurrentflow throu'ghapola-r relayl at" offic'ea This will operate relay t and its d'peratien will clese' circuit H to perate-e supervisory signal at offibe'm' The" foregoing type offlineis well known in the art and has been described ine'r el y' te illustrate 6118' epeeifie' type o'f line" v Whidh} the arrangements (if the i'nli'ntibfi are applicable; 'Howvr, understand that tnearrangements bf'tfi iflvii'tibii' are applicable relay 4 the mer'gmar relay 6- operate at nals at the ofilces and prevent normal supervisory signaling between such ofiices. Accordingly in accordance with the arrangements of this invention there would be connected across line L at one of the oflices, such as A, a high resistance I6,.which might be two megohms. resistance would be connected to the grid of a vacuum tube II. The filament of tube I! would be grounded and a responsive device, such as relay I8, connected in the plate circuit of the tube. Under such condition there would exist; an arrangement such as is shown schematically in Fig. 2 when key is closed. As battery 5 is connected to the grid of the tube and is grounded,

and as the filament of the tube is grounded, the

battery 5 and a portion of resistance I6 will be connected between the filament and grid, as

shown in Fig. 2, and a potential will be thus applied to the grid which will be sufilciently negative to block the tube. Such an arrangement would have no effect on the normal transmission of supervisory signals between oflices A and B. If it should now be desired to send a signal in addition to normal supervisory signals between the oillces the circuit I2 at oifice B would be closed and relay ,ed it will not be connected betweenthe grid and filament of the tube I! and will have no effect on the potential on the grid. The removal of grounded battery 5 from the line will, however,

remove the negative bias from the grid of the tube and allow current to now in the plate circuit, of

the tube to operate relay I8. The relay I8 might control any kind of a responsive device, such as a telegraph sounder or the alarm arrangements shown. In the arrangements shown, the operation of relay I8 would operate the buzzer I9. This would indicate to the operator at oflice A that the circuit I2 at ofiice B had operated. As pointed out heretofore, circuit I 2 might be operated by an alarm device at ofiice B. Upon the operation of the buzzer IS the operator at ofllce A could operate key K. This would short-circuit the buzzer and operate lamp 2 I. When the circuit I2 at oflice B is now opened, relay I3 will release. This will disconnect non-grounded battery I5 from the line and reconnect grounded battery 5 to the line. .This will again put a negative bias on the grid of tube I1 and cause it to be blocked. This will release relay I8 and open the circuit of the lamp 2 I The buzzer I9 would now be operated over the left-hand contact of key K. The key K would now be restored to normal to restore the alarm or responsive apparatus atofiice A to, normal, It is The mid-point of this pointed out that relay I3 disconnects grounded battery 5 from the line L and connects nongrounded battery I5 thereto over make-beforebreak contacts so that there will be no interruption of the continuity of current flow for supervisory signaling purposes over the line.

.While the invention has been disclosed as embodied in certain specific arrangements which are deemed desirable it is understood that it is capable of embodiment in many other and widely varied forms without departing from the spirit of v the invention as defined by the appended claims.

What is claimed is:

1. A circuit over which supervisory signals are transmitted, means at one end of the circuit for connecting grounded battery thereto to provide current for the operation of said supervisory signals, a. resistance bridged across the other end of said circuit, a vacuum tube having its grid so connected to said resistance that a negative potential sufiicient to render said tube inoperative will be applied to said grid by said grounded battery when it is connected to said circuit, means for disconnecting said grounded battery from said circuit whereby said negative potential will be removed from the grid of said tube and it will be rendered operative and. for simultaneously connecting a nongrounded battery to'said circuit to provide current for the operation of said supervisory signals, and responsive means controlled by said tube.

2. A circuit over which supervisory signals are transmitted, means at one end of the circuit for connecting grounded battery thereto to provide current for the operation of said supervisory signals, a resistance bridged across the other end of said circuit, a vacuum tube having its grid so connected to said resistance that a negative potential sufficient t render said tube inoperative will be applied to said grid by said grounded battery when it is connected to said circuit, a signaling .circuit associated with said first circuit at the end thereof where said grounded battery is located, means controlled by said signaling circuit for disconnecting said grounded battery from said first circuit whereby said negative potential will be removed from the grid of said tube and it will be rendered operative and for simultaneously connecting a, non-grounded battery to said first circuit to provide current for the operation of said supervisory signals, and a second signaling circuit controlled by said tube.

- 3. A circuit over which supervisory signals are transmitted, a relay having make-before-break contacts associated with one end of said circuit,

.a grounded battery normally connected to said circuit over the break contacts of said relay, a high.resistance bridged across the other end of said circuit, a vacuum tube having its filament grounded and its grid so connected to said resistance that a negative potential sufiicient to render said tube inoperative will be applied to said grid by said grounded battery when it is connected to said circuit by said relay, said tube being adjusted to be operated in the absence of said negative potential on its grid, a non-grounded battery adapted to be connected to said line over the make contacts of said relay when operated, a signaling circuit for operating said relay and a second signaling circuit controlled by said tube. I

4. A loop dial trunk interconnecting a community dial oflice and a central office, a grounded common battery at said community dial cffice normally connected to said loop dial trunk, supervisory signaling means at each of said ofiices controlled by said last mentioned alarm circuit for trolledvby current from said grounded common battery, a high resistance bridged across said trunk atsaid central ofllce, a vacuum tube having its filament grounded'and its grid connected to said resistance wherebythe connection of said i Y grounded common battery to said trunk will cause a negative potential to be placed on said grid sufflcient to render said tube inoperative, an alarm device controlled by said tube, a non-grounded battery at said community dial ofiice, an alarm circuit at said community dial ofiice responsive to a failure of equipment 'thereat, and means condisconnecting said, grounded battery from said trunk whereby said negative potential will be removed from said grid to render said tube operative and to operate the alarm circuit controlled bysaid tube, said last mentioned meansalso operating tosimultaneously connect said non-grounded CHARLES S. RHOADS. 

